ABSTRACT
The growing interest in field experimentation introduces the problem of getting the undivided attention of people for studies that require persuasive communications and the like. Passersby on streets and other public areas frequently are not willing to be delayed, and those who are willing to stop and listen to an experimenter’s spiel may well have particular personality characteristics. Whenever a subject population is restricted in some way, as when certain per sonality types are overrepresented, the experimenter must be careful in generalizing the conclusions of the experiment to the population at large.
